Early onset periodontitis (EOP) encompasses a number of periodontal diseases in children and adolescents that result in rapid destruction of the periodontal attachment apparatus leading to pronounced tooth loss. The prevalence of EOP was estimated to be 0% among African-American, 5% among Hispanic, and 1.3? among white adolescents in a national survey among U.S. school children between the ages of 13-17, and 2.1% among the same age group studied as part of NHANES III. Although risk factors for EOP were investigated, relationships between EOP and the microbiological and clinical characteristics of the moth, and effects of the primary dentition and systemic health of children are unknown. Moreover, the occurrence of EOP in systematically compromised children, such as those with human immunodeficiency virus (HIV infection), remain unexplored. We propose a 3 year cross-sectional study to assess the correlates of, and specific risk factors for EOP, and to investigate the clinical features, microbial patterns of transmission, and risk to oral and systemic health associated with EOP in Senegal,, a site where we currently have ongoing studies among women who have on average 5 children between the ages of 4 and 17, in order to evaluate the following specific aims: (1) Determine specific risk factors for EOP in a Senegalese pediatric population by evaluating demographic factors, health history of both the child and mother, and findings from comprehensive oral examinations including measurements of gingival inflammation and decayed, missing and filled teeth; and (2) Compare the prevalence of specific periodontal bacterial pathogens, and the immune responsiveness to those pathogens among children with and without EOP. Furthermore, we propose to assess whether children of moths with specific periodontal bacteria have comparable microbial patterns, and compare children with and without EOP with respect to humoral immune response to specific periodontal pathogens. We will examine 1,100 Senegalese children of mothers currently being followed in ongoing studies. Presence of EOP will be assessed by probe measurements of all teeth, exclusive of the third molars. Mothers will undergo a standardized interview, and children will undergo oral examination and have paperpoint and blood samples collected. Bitewing radiographs (among children greater than 3 years of age with EOP) will be taken to assess the degree of bone loss. The proposed study will contribute important information which may be useful in designing strategies to prevent periodontitis.